7M}? LHE JOUKNAL ORVGPOLOGY.. 
felsite, sericite-schists, conglomerates, altered traps, hornblende-schists 
and other green schists. Occasionally contained in them are areas of 
banded jasper and hematite. On the north side of Cache Bay is a 
felsitic conglomerate in contact with a coarse-grained hornblende- 
granite. Beds of dolomite are associated with this conglomerate. The 
breadth of the Keewatin series gives no certain criterion by which to 
estimate its thickness. The dip shows an apparently simple synclinal 
structure. 
As to the relations of the Laurentian to the Huronian series, they 
have a general parallel schistosity, and there are many phenomena 
suggestive that the granitic and syenitic type is of igneous eruptive 
origin, later than the Huronian, but the hornblendic and micaceous 
phases of these granites may be rocks of different determinable ages, 
the discovery of which may throw light not only on the genesis of the 
Laurentian, but on its relations to the overlying Couchiching and 
Keewatin. Cutting both Laurentian and Couchiching rocks are 
diabase dikes in such attitudes as to leave little doubt that they were 
intruded since the last folding, on which assumption their geological 
age is post-Keewatin. 
Grant,’ in 1894, gives a general account of the geology of the 
Gunflint lake district. In Ts. 65 and 66 N., Rs. 4, 5 and 6 W., are 
Keewatin rocks, including the usual types—volcanic tuff, greenstone- 
schists, greenstone, and the Ogishke conglomerate. The Saganaga 
granite is intrusive in the Keewatin. The more crystalline schists 
of the district have been called Couchiching and Vermilion. It, 
however, appears that these rocks in this area are a more crystalline 
phase of the Keewatin, and that they owe their crystalline nature to the 
proximity of intrusive granite. 
The iron-bearing rocks of Akeley Lake lie upon the Keewatin 
greenstone to the north, and on the south are overlaid by the great 
gabbro mass. The belt has a width of from 300 to 1300 feet, and a 
dip varying from 20° to almost vertical, but averaging 45° to 50°. 
Where widest, it has an average dip of 30°, which would make a maxi- 
mum thickness of 650 feet. The iron ore is a titaniferous magnetite. 
The Animikie rocks are little disturbed, except locally, having an 
* Preliminary Report of Field Work during 1893 in Northeastern Minnesota, by 
U.S. Grant, 22d Ann. Rep. Geol. and Nat. Hist. Sur. of Minn, Part IV., pp. 67-78, 
1894. 
